Latching mechanism



Sept. 20, 1938. w. T. PARKER 2,130,856

LATCHING MEGHANISM Filed Dec. l, 1957 3 Sheets-Sheet 1 Sept. 20, 1938.w. T. PARKER LAICHING MECHANISM Filed Dec. l', 1937 3 Sheets-Sheet 2INVENTOR M//V/ma Z'Pczr/rer:

BY v @194 /WMA ATTOR Y Sept. 20, 1938. w. T. PARKER 2,130,856

LATCHING MECHANISM ffy wlTNEssEs: 52 INVENTOR ZM/M i? VVV/ard ZUDar/efPatented Sept. 20, 1938 UNITED STATES PATENT OFFICE LATCHING MECHANISMPennsylvania Application December 1, 1937, Serial No. 177,601

13 Claims.

'I'he invention relates to circuit breakers in general and moreparticularly to latching mechanisms for circuit breakers.

An object of the invention is the provision of '6 an improved latchingmechanism for a circuit breaker that is simple, reliable in operation,and inexpensive to manufacture.

Another object of the invention is the provision of a latching mechanismfor releasably holding the contact members of a circuit breaker inclosed position, that requires fewer parts than has heretofore beenconsidered necessary for breakers of the same or comparable size andrating.

Another object of the invention is the provision of an improved latchingmechanism for a circuit breaker that offers a relatively smallresistance to relatching of the breaker actuating means and yet which iscapable of positively holding the breaker closed against the force of apowerful opening bias.

Another object of the invention is the provision of a circuit breaker ofthe trip free type with an improved latching mechanism that offers avery small resistance to the retrieving of the breaker actuating meansto its latched position thus permitting the use of less powerfulretrieving springs to insure retrieving, and also reducing the totalenergy required to reclose the breaker.

The novel features that are considered characteristic of the inventionare set forth in particular in the appended claims. The inventionitself, however, both as to structure and operation, together withadditional objects and advan- 25 tages thereof will be best understoodfrom the following detailed description of one embodiment thereof whenread in connection with the accompanying drawings in which:

Figure 1 is a view partly in side elevation and .gli partly in sectionillustrating the latching mechanism constructed in accordance with theinvention as applied to the operating mechanism of a circuit breaker.

Fig. 2 is a plan view of the latching mecha- 4e nism in conjunction withthe trip free elements of the actuating mechanism of the breaker.

Fig. 3 is a sectional view taken substantially along the line III--IIIof Fig. 2 showing the latching mechanism in latching position.

Fig. 4 is a fragmentary sectional view similar to Fig. 3 illustratingthe latching mechanism at a stage ofthe tripping operation immediatelyfollowing release of the actuating means.

Fig. 5 is a fragmentary sectional view similar 55 to Fig. 4 illustratingthe latching mechanism at a stage of the retrieving operation of theactuating means; and,

Figs. 6 and 7 are fragmentary side elevational views illustrating thelevers of the actuating means in the tripped and retrieved positions re-5 spectively.

The present invention constitutes an improvement and further developmentof the mechanism disclosed in the copending application of J. B.MacNeill and John W. May, Serial No. '79,670 10 which is assigned to theassignee of this invention.

Referring to the drawings and particularly Figure 1 thereof, the latchmechanism, indicated generally at 9, is shown mounted in operative po-15 sition on an operating mechanism I I of a circuit breaker.

The operating mechanism II is of the same general construction as theoperating mechanism shown and described in the above mentioned co- 20pending application of J. B. MacNeill and John W. May, and comprises, ingeneral, a frame I3 on which is mounted an operating electromagnet I5,and a trip-free lever mechanism indicated generally at I'I whichnormally serves to con- 25 nect the circuit breaker (not shown) to theoperating electromagnet I5.

The operating electromagnet I5 is in the form of a solenoid andcomprises a movable core I9,

a cooperating stationary core (not shown) and 30 an operating winding2|, which, when energized, pulls the movable core downwardly toward thestationary core to effect a closing operation of the circuit breaker.

The trip-free lever mechanism comprises a pair of spaced parallel andrigidly connecting operating levers 23 pivoted on the frame I3, and apair of spaced parallel and rigidly connected actuating levers 25 whichare pivoted to the free ends of the operating levers 23. The operatinglevers 25 are rigidly connected together by means of a brace 21extending between the levers adjacent their lower edges. The operatinglevers 25 are pivoted for rotation on the frame I3 by means of a pair ofpivot pins 29 (Fig. 2). 45

The actuating levers 25 are pivotally connected adjacent their one endto the free ends of the operating levers 25 by means of a pivot pin 3|which extends transversely through the ends of the levers 23 and 25. Thelevers 25 are rigidly `50 connected together by means of a brace 33which extends between the levers, and the levers 25 are spaced so as tobe movable into the space between the outer operating levers 25.

The contact members (not shown) of the circuit breaker are connectedthrough a rod 35 to the actuating levers 25 intermediate their ends bymeans of a pivot pin 31 which extends between the levers 25. Theactuating levers t5 carry a trip-free bar or roller 39 which extendstransversely between the free ends of the levers 25 and which is adaptedto be normally engaged by the latching mechanism 9 as will be explainedhereinafter.

When in the closed circuit position shown by the full lines in Fig. l,the operating levers 23 are biased for movement in a clockwise directionabout their pivot axis 25 by means of a retrieving spring lll positionedbetween the levers 23 and the frame I3. One end of the spring ll ispivotally anchored by means of a bracket 43 to the levers 25 while theother end of the spring abuts the end of the frame i3 and is maintainedin that position by any suitable means.

A latch member l5 is pivotally carried by the frame E3 and is biased bymeans of a spring 41 to a latching position for engaging the pivot pin3l which connects the ends of the levers 23 and 25 to retain them in theclosed circuit position shown in the full lines 'in Fig. l. In order tocause the latch 45 to release the pivot pin 3l and the operating levers23 during a tripping operation of the mechanism, the actuating leverscarry a projection 49 adjacent the pivot pin 3l for engaging acooperating projection 5i carried by the latch 45. As the actuatinglevers 25 move to the position .shown by the dotted lines in Fig. lunder the influence of the opening bias of the breaker, following theirrelease, the projection 139 carried thereby engages the cooperatingprojection 5l and moves the latch member 45 to its released positioncausing the latch i5 to release the pivot pin 3i and the free ends ofthe operating levers 23. The reactive force of the compressed retrievingspring lil then rotates the operating levers 23 in a cooperatingdirection about their pivot axis 29 to the open circuit position shownby the dotted lines in Fig. 1. During this movement of the operatinglevers 23, the actuating levers 23 are rotated by the operating levers23 in a clockwise direction about the pivot pin 31 which has reached theupper limit of its movement when the breaker has reached its full opencircuit position. The clockwise rotation by the operating levers 23returns the free ends of the actuating levers 23 and the trip-free baror roller 39 to their latched position as shown in Fig.

7, to be reengaged and latched by the latching4 mechanism Q. Theactuating levers 23 are thus automatically retrieved to their latchedposition following each release thereof.

In order to actuate the mechanism to a closed circuit position, theoperating levers 23 are connected to the movable core i9 of theoperating electromagnet l5 by means of a pivot link 52 which ispivotally connected at its lower end to the movable core i9 by means ofa pivot pinl 53. The upper end of the link 5l is pivotally connected tothe operating levers 23 intermediate their ends by means of a pivot pin55.

When the electromagnet l5 is energized, the movable core l and theconnecting link 52 are moved downwardly to rotate the operating levers23 and the connected actuating levers 25 in a counterclockwise directionabout the pivot pins 29 and the trip-free roller 33, respectively fromthe position shown in Fig. '7 to the closed circuit position shown inthe full lines in Fig. l of the drawings.

When the free ends of the actuating levers 25 and the trip-free roller39 are held in latched position by the latching mechanism 9, the axis ofthe roller 39 which forms the normal pivot axis of the actuating levers25 is aligned with the axis of the pivot pins 29 which form the pivotaxis of the operating levers 23 and the latch serves as a fulcrum pointfor the actuating levers 25 to connect the breaker to the operatinglevers 23 for operation thereby.

The brace 21 which connects the operating levers 25 serves as a stop toprevent movement of the actuating levers 25 below the operating levers25 during the retrieving operation and to vcause the trip free roller 39to align with the pivot pins 29 when the levers are in the positionshown in Fig. 7.

The latch mechanism 9 comprises a main latch member 51 biased to alatching position in which it engages and restrains the trip-free roller39 and the actuating levers 25 in latched position shown in Fig. 3 andin the full lines as shown in Fig. l. The latch member 51 is pivotallycarried on the frame I3 by means of a pivot pin 59 and is biased to itslatching position by means of a compression spring 6| interposed betweenthe latch member 51 and a cross piece 63 of the frame i3. r)The ends ofthe spring 6| are seated in suitable cylindrical recesses or wells (notshown) provided in the latch member 51 and the cross piece (i3. Thecross piece G3 has a surface 64 which forms a stop to prevent movementof the latch 51 beyond its latched position as shown in Fig. fi.

In order to hold the latch 51 in its latching position against theupward bias produced on the actuating levers 25 by the bias of thecircuit breaker, a second latch member in the form of a lever 65 isprovided. The second latch member 55 is pivotally mounted at one end ofthe frame E3 by means of a pivot pin 51. The inner end of the secondlatch member 65 is provided with a substantially right angle notch 69for engaging a cooperating surface 1Q on the main latch 51 to hold themain latch in its latching position. It will be noted that the point ofengagement of the second latch 65 with the latch 51, and the pivot axisof the latch 55 in the latching position thereof lie in a line which issubstantially at right angles to the direction of movement of the mainlatch 51 so that the latch member 65 alone in its latching positioneffectively locks the main latch 5l in its latching position. The latchmember 65 is biased to its latching position by means of a light coilcompression spring 1l which exerts a very small force on the secondlatch member for returning it to its latched position during resettingof the latching mechanism.

The second latch member G5 is adapted to be moved to its releasedposition to effect a tripping operation of the latching mechanism andoperating mechanism by a tripping means indicated generally at 13. rIhetripping means 13 is carried by the frame i3 and comprises a trippingelectromagnet 15 including a movable core 11. The tripping electromagnet15 is adapted to be energized in response to predetermined abnormalconditions to move the movable core 11 in an upward direction duringwhich movement it strikes the second latch member 65 and moves it toreleased position to ei'fect release of the main latch member 51 andtripping of the operating mechanism and circuit breaker.

The movable core 11 of the tripping electromagnet is also adapted to beactuated in an upward direction manually by the operation of a manuallyoperated lever 19 pivotally carried on the frame I3. The end of themanual tripping lever 19 is adapted to engage an intermediate member 8|which is slidably mounted on a guide bolt 83. 'The intermediate member9| is also guided by means of a pair of guide members 85. Theintermediate member 8| is moved by the manual tripping lever 19 in anupward direction to engage and move the movable core 11 upwardly toeiect tripping of the latch mechanism and operating mechanism in thesame manner as when the electromagnet 15 is energized.

The main latch 51 has its upper surface rounded as indicated at 81 toprovide a cam surface for cooperating with the trip-free roller 39during the retrieving movement thereof. As the trip-free' roller 39 ismoved downwardly to its latched position during a retrieving operation,it engages the rounded cam surface 81 of the latch member 51 and forcesthe latch member in a clockwise direction about its pivot axis 59 toreleased position as shown in Fig. 5, thus allowing the trip-free rollervto clear or move below the nose of the latch 51. When the trip-freeroller 39 reaches its latched position, the biasing spring 6| returnsthe latch member 51 to its latching position to reengage the roller 39.

To insure complete retrieving of the actuating levers 25 and thetrip-free roller 39 to latched position, it is necessary that the secondlatch member 65 be maintained in its released position 4free of the mainlatch member 51 until the actuatingV levers 25 and trip-free roller 39are retrieved to their latched position. Otherwise, the trip-free roller39 would jam against the top of the main latch member 51 during aretrieving operation.

For holding the second latch member 65 in its released position free ofthe main latch 51 during release and retrieving of the actuating levers25 and the trip-free roller 39, there is provided a lever 89 which ispivoted on the pivot pin 61 of the second latch member 85. The lever 99consists oiV two arms 9| and 93 (Fig. 2) which are rigidly connected formovement together by means of a pin 95. 'I'he ends of the arms 9| and 93are in pivotal engagement with the pin 61. The arm 9| of the lever 89 isof greater length than the arm 93 and has a projecting portion 96, theend 91 of which is bent inwardly so as to lie in the path of the nalretrieving movement of one of the actuating levers 25 so as to beengaged thereby during the nal retrieving movement and in the retrievedposition of the actuating lever 25. The lever 89 is biased in aclockwise direction by means of a light coil compression spring 99 whichis interposed between the cross pin 95 and the frame I3. The lever 89 isheld in inoperative position by the actuating levers 25 when theactuating levers are in their latched position as shown in Fig. 3 toallow the second latch member 65 to engage and hold the main latchmember 51 in its latched position. When the latching mechanism 9 isoperated by the tripping means 13 to release the trip-free roller 39 andthe free ends of the actuating levers 25, the free ends of the levers 25move in an upward direction and disengage the lever 89. The lever 99,when disengaged by the actuating levers, is moved in a clockwisedirection about its pivot axis 61, and the cross pin 95 thereof engagesand holds the second latch member 65 in its released position as shownin Figs. 4 and 5. The biasing spring 99 is of suicient strength to causethe lever 89 to hold the second latch member 65 in its released positionagainst the bias of the return spring 1|.

During retrieving of actuating levers 25 after the trip-free roller hassubstantially cleared the nose of the latch member 51, the end of one ofthe actuating levers 25 engages the inwardly bent end 91 of the level`89 and forces the lever 89 in a counterclockwise direction about itspivot axis 6'1 to an inoperative position allowing the second latchmember 65 to be returned to its latching position in engagement with themain latch member 51 by means of the return spring 1|.

Since the second latch member 65 in its latching position is alonesuiflcient to hold the main latch 51 in latching position to hold thebreaker closed against its bias, the biasing spring 6| of the latch 51need only be strong enough to exert sufficient force to return the latchmember 51 to its latching position with the required speed, and sincethe biasing spring 99 of the holding lever 89 need only be strong enoughto hold the second latch member 65 in its released position against thebias of its light return spring 1|, the springs 6| and 99 oier only avery small resistance to the return or the retrieving movement of theactuating levers 25. This permits the use of a smaller and less powerfulretrieving spring for causing retrieving of the actuating levers, andthus reduces the total amount of energy required for operating themechanism to close the circuit breaker.

The operation of the mechanism is briey as follows: With the mechanismin the closed and latched position as shown in full lines in Fig. l, theoperation of the tripping means 13, either in response to predeterminedelectrical conditions or by the manual operating lever 19 lifts themovable core 11, causing it to strike and move the second latch member65 to its released position as shown in Fig. 4. The movement of thesecond latch member 65 to its released position releases the main latchmember 51 and since this member alone is insufficient to hold themechanism and breaker in closed position, the inner actuating levers 25are rotated in a counter-clockwise direction by the bias of the breaker,forcing the main latch member 51 to its released position. As the freeends of the actuating levers 25 move upwardly, they disengage andrelease the biased lever 89, allowing the lever to move in a clockwisedirection to engage and hold the second latch member 65 in its releasedposition. The actuating levers 25 are rotated by the biasing action ofthe breaker to the position shown in Fig. 6 and by the dotted lines inFig. l. At this point the breaker is in full open position. Duringupward movement of the actuating levers the projection 49 carriedthereby moves the latch member 45 to released position releasing thefreeends of the operating levers 23. When released, the operating members 23are moved in a clockwise direction about their xed pivot axis 29 by theretrieving spring 4| to the open circuit position shown in Fig. 7 and bythe dotted lines in Fig. l. The upward movement of the operating levers23 causes the actuating levers 25 to be rotated in a clockwise directionabout the pivot pin 31 to the retrieved position shown in Fig 7. Duringthe retrieving movement of the actuating levers 25, the trip-free roller39 is moved to its latched position and is reengaged by the main latchmember 51. As the tripfree roller approaches its latched position andclears the main latch 51, the free end of one of the actuating levers 25engages and moves the latch holding lever 89 to its inoperative positionallowing the second latch member 55 to return to its latching positionin holding engagement with the main latch member 51.

To close the breaker, the operating electromagnet l5 is energized topull the movable core I9 and connecting link 52 downwardly. The downwardmovement of the core I9 and the connecting link 52 rotates the connectedoperating levers 25 and actuating levers 23 in a counter-clockwisedirection from the position shown in Fig. '7 to the position shown bythe full lines in Fig. l. As the levers 23 and 25 approach closedposition the pin 3l forces the latch member (l5 to its released positionin clearing the same. When the levers 23 and 25 reach their fully closedposition as shown in the full lines. in Fig. l, the latch member 45 ismoved to its latching position by the spring ll to hold the levers inclosed position.

While the invention has been disclosed in accordance with the provisionsof the patent statutes, it is to be understood that various changes maybe made in the structural details thereof without departing from thespirit of the invention. It is desired, therefore, that the accompanyingclaims be given the broadest reasonable construction possible in thelight of the prior art.

I claim as my invention:

l. In a latching mechanism for a circuit breaker provided with a biasedactuating member releasable to effect opening of the circuit, incombination, a main latch biased to a latching position for engaging andrestraining said actuating member in a predetermined position, a secondlatch having a latching position for holding said main latch in itslatching position, said second latch being biased to its latchingposition, and a spring biased means controlled by said actuating memberfor maintaining said second latch in released inoperative position untilsaid actuating member is returned to said predetermined positionfollowing each release thereof.

2. In a latch mechanism for a circuit breaker provided with an operatingmechanism including a biased trip free member releasable to effectopening of the circuit, in combination, a main latch biased to alatching position for engaging and restraining said trip free member ina predetermined position, a second latch having a latching position forengaging and holding said main latch in latching position, said secondlatch being biased to its latching position, and a spring biased membercontrolled by said trip free member for maintaining said second latch inreleased inoperative position until said trip free member is returned tosaid predetermined position following each release thereof.

3. In a latching mechanism for a circuit breaker provided with a biasedactuating member releasable to effect opening of the circuit, incombination, a main latch biased to a latching position for engaging andrestraining said actuating member in a predetermined position, a secondlatch having a latching position for engaging and holding said mainlatch in latching position, said second latch being biased to itslatching position, and a spring biased member engaged and held in aninoperative position by said actuating member in its predeterminedposition, said spring biased member being operable when released by saidactuating member to maintain said second latch in released positionuntil said actuating member is returned to its predetermined position.

4. In a latching mechanism for a circuit breaker provided with a biasedactuating member releasable to eifect opening of the circuit, incombination, a main latch biased to a latching position for engaging andrestraining said actuating member in a predetermined position, a secondlatch having a latching position in which it engages and holds said mainlatch in latching position, said second latch being biased with arelatively light force to its latching position, a spring biased memberoperable to hold said second latch in released position when theactuating member is released and until it is returned to'saidpredetermined position, said spring biased member being engaged andmoved by said actuating member to an inoperative position against itsbias when said actuating member is returned to said predeterminedposition, the spring bias of said holding member being suflicient tohold said second latch in released position but oifering only a smallresistance to the return movement of said actuating member to saidpredetermined position.

5. In a latching mechanism for a circuit breaker provided with a biasedactuating member releasable to effect opening of the circuit, incombination, a frame, a main movable latch biased to a latching positionfor engaging and restraining said actuating member in a predeterminedposition, a second movable latch having a latching position for engagingand holding said main latch in its latching position said second latchbeing biased to its latching position, tripping means operable to movesaid second latch to released position to effect release of said mainlatch and actuating member, and means carried by said frame andcontrolled by said actuating member for holding said second latch in itsreleased position until said actuating member is returned to saidpredetermined position following each release thereof.

6. In a latching mechanism for a circuit breaker provided with a biasedactuating member releasable to effect opening of the circuit, incombination, a frame, a main movable latch biased to a latching positionfor engaging and restraining said actuating member in a predeterminedposition, a second movable latch having a latching position for engagingand holding said main latch in its latching position said second latchbeing biased to its latching position, tripping means operable to movesaid second latch to released position to effect release of said mainlatch and actuating member, said actuating member when returned to itspredetermined position forcing said main latch back to its releasedposition to clear the same prior to being relatched thereby when itreaches said predetermined position, and means carried by said frame andcontrolled by said actuating member for holding said second latch in itsreleased position clear of said main latch until said actuating memberis returned to said predetermined position following each releasethereof.

7. In a latching mechanism for a circuit breaker provided with a biasedactuating member releasable to effect opening of the circuit, incombination, a main latch biased to a latching position for engaging andrestraining said actuating member in a predetermined position, a secondlatch having a latching position for engaging and holding said mainlatch in its latching position said second latch being biased to itslatching position, tripping means operable to move said second latch toreleased position to effect release of said main latch and actuatingmember, and a pivoted spring biased lever engaged and held in aninoperative position by said actuating member in its predeterminedposition, said lever being operable when released by said actuatingmember as it moves away from its predetermined position to engage andhold said second latch in released position until said actuating memberis returned to its predetermined position.

8. In a latching mechanism for a circuit breaker provided with a biasedactuating member releasable to effect opening of the circuit, incombination, a main latch biased to a latching position for engaging andrestraining said actuating member in a predetermined position, a secondpivotally mounted latch having a latching position for engaging andholding said main latch in latching position, said second latch beingbiased with a light force toits latching position, tripping meansoperable to move said second latch to released position to effectrelease of said main latch and actuating member, and a lever pivotedabout the same axis as the second latch and controlled by said actuatingmember for holding said second latch in released position until saidactuating member is returned to its predetermined position followingeach release thereof.

9. In an operating mechanism for a circuit breaker, a trip free memberreleasable from a predetermined position to effect opening of thebreaker, means for automatically returning said member to itspredetermined position following each release thereof, operating meansoperable to close said breaker only when said member is held in saidpredetermined position, in combination, a main latch biased to alatching position for engaging and restraining said member in itspredetermined position, a second latch having a latching position forengaging and holding said main latch in latching position, said secondlatch being biased to latching position, trip means operable to movesaid second latch to released position to effect release of said mainlatch and trip free member, and a spring biased member engaged and heldin an inoperative position by said trip free member in its predeterminedposition said spring biased member being operable when released toengage and hold said second latch in released position until said tripfree member is returned to its predetermined position to allow said tripfree member to clear said main latch as it returns to said predeterminedposition.

10. In an operating mechanism for a circuit breaker, a trip free memberreleasable from a set position to effect opening of the breaker, meansfor automatically resetting said member to its set position followingeach release thereof, operating means operable only when said member isheld in its set position to close the breaker, in combination, a frame,a main latch biased to a latching position for engaging and restrainingsaid trip free member in its set position, a second latch having alatching position for engaging and holding said main latch in latchingposition, said second latch being biased to its latching position, tripmeans operable to move said second latch to released position to effectrelease of said main latch and trip free member, and means carried bysaid frame and controlled by said trip free member for holding saidsecond latch in released position until said trip free member is resetto its set position following each release thereof to allow said tripfree member to clear said main latch during resetting of said trip freemember.

11. In an operating mechanism for a circuit breaker, a trip free memberreleasable from a set position to effect opening of the breaker, meansf'or automatically resetting said member to its set position followingeach release thereof, operating means operable only when said member isheld in` its set position to close the breaker, combination, a mainlatch biased to a latching position for engaging and restraining saidtrip free member in its set position, a second latch having a latchingposition for engaging and holding said main latch in latching position,said second latch being biased to its latching position, trip meansoperable to move said second latch to released position to effectrelease of said main latch and trip free member, and a spring biasedpivoted lever engaged and held in an inoperative position by said tripfree member in its set position, said lever being operable when releasedby said trip free member as it moves away from set position, to engageand hold said second latch in released position until said trip freemember is returned to its set position.

12. In an operating mechanism for a circuit breaker, a. trip free memberreleasable from a set position to effect opening of the breaker, meansfor automatically resetting said member to its set position followingeach release thereof, operating means operable only when said member isheld in its set position t0 close the breaker, in combination, a mainvlatch biased to a latching position for engaging and restraining saidtrip free member in its set position, a pivoted second latch having alatching position for engaging and holding said main latch in latchingposition, said second latch being biased to its latching position, tripmeans operable to move said second latch to released position to effectrelease of said main latch and trip free member, and means including alever pivoted about the same axis as said second latch and controlled bysaid trip free member for holding said second latch in released positionuntil said trip free member is reset to its set position following eachrelease thereof.

13. In a latching mechanism for a circuit breaker operating mechanismprovided with a trip free retrieving actuating member releasable from alatched position to effect opening of the circuit and automaticallyresettable to its latched position following each release thereof, incombination, a main latch biased to a latching position for restrainingsaid actuating member in latched position, a second latch having alatching position for holding said main latch in latching position, saidsecond latch being biased by a light force to its latching position, anda spring biased member operable to hold said second latch in releasedposition until said actuating member is returned tr its latched positionfollowing each release thereof, said spring biased member being engagedand held in an inoperative position by said actuating member when in itslatched position.

WILLARD T. PARKER.

